The Piaggio P.XII is an Italian 18-cylinder radial aircraft engine developed in the 1930s by Rinaldo Piaggio S.p.A. The P.XII was two Piaggio P.X engines in tandem, which were versions of the French Gnome-Rhône 9K Mistral made under license, themselves being much modified Gnome-Rhône 9A - a license-built Bristol Jupiter.

The engine was used in some Italian aircraft from 1940 until the end of World War II, especially the Piaggio P.108. An up-rated version was tested as the Piaggio P.XXII.

Variants of the Piaggio P.XII include: (R - Riduttore - reduction gearing and C - Compressore - supercharged)

P.XII R.C.35

(geared, rated altitude 3,500 m (11,500 ft))

P.XII R.C.40

(geared, rated altitude 4,000 m (13,000 ft))

P.XII R.C.100/2v

(geared, rated altitude 10,000 m (33,000 ft))

P.XV R.C.60/2v

(geared, rated altitude 6,000 m (20,000 ft))

P.XXII R.C.35D

Higher rating with slightly higher displacement than the P.XII series engines. (geared, rated altitude 3,500 m (11,500 ft))

P.XXII R.C.35R

Same as P.XXII R.C.35D, but propeller rotates in opposite direction

P.XXII R.C.60

(geared, rated altitude 6,000 m (20,000 ft))

• CANT Z.1015
• CANT Z.1018
• CANT Z.511
• Caproni Ca.169
• Piaggio P.108
• Savoia-Marchetti SM.84
• Savoia-Marchetti SM.89

Data from Aircraft Engines of the World 1945.^[1]

• Type: 18-cylinder air-cooled radial engine
• Bore: 146 mm (5.75 in)
• Stroke: 176 mm (6.93 in)
• Displacement: 53 L (3,200 cu in)
• Length: 1,700 mm (66.93 in)
• Diameter: 1,410 mm (55.51 in)
• Dry weight: 850 kg (1,874 lb)
• Frontal Area: 1.56 m² (16.8 sq ft)

• Valvetrain: 2 x overhead valves per cylinder operated by rockers and pushrods
• Supercharger: Centrifugal compressor, geared to 7.81:1
• Fuel system: Single Piaggio downdraught carburettor with automatic boost and mixture control
• Fuel type: 87 octane
• Oil system: Pressure fed at 482.6 kPa (70 psi), dry sump
• Cooling system: Air
• Reduction gear: Epicyclic reduction gear, gear ratio: 0.62:1
• Starter: Garelli compressed air starter
• Ignition: 2x Marelli AQ18 magnetos, 2 x spark plugs per cylinder fed by a shielded ignition harness.

• Power output: Take-off: 1,500 hp (1,100 kW) at 2,100rpm
• Military: 1,350 hp (1,010 kW) at 2,100rpm at 3,500 m (11,500 ft)
• Cruising: 1,000 hp (750 kW) at 1,700rpm at 3,500 m (11,500 ft)
• Specific power: 22.29 kW/L (0.49 hp/cu in)
• Compression ratio: 6.5:1
• Specific fuel consumption: 0.2795 kg/kW/hr (0.46 lb/hp/hr)
• Oil consumption: 0.0134 kg/k/w/hr (0.022 lb/hp/hr)
• Power-to-weight ratio: 1.324 kW/kg (0.8 hp/lb)

• Gnome-Rhône 18L
• Tumansky M-90

Related lists

• List of aircraft engines

• Gunston, Bill. World Encyclopedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9
• Wilkinson, Paul H.. Aircraft Engines of the World. 1941